Reflectors compared to UDP amplification attack campaigns, as recentlyĭemonstrated during attacks in Turkey, Italy and South Korea. While there are different motivations and objectives behind these attackĬampaigns, there is a noticeably higher rate of collateral damage among the Independent research in the behavior of a multitude of systems and devices on the internet exposed more than 4.8 million devices vulnerable to an average amplification factor of 112x and thousands of hosts that could be abused for amplification up to a factor of almost 80,000x, respectively, reflect more than 5,000 packets within 60 seconds, causing a serious impact on a victim’s network. The default setting for Linux systems (_synack_retries kernel variable) is five while the documentation advises against settings higher than 255. The amount of amplification depends on the number of SYN-ACK retransmits by the reflection service, which is typically governed by a configurable parameter. Retransmit the SYN-ACK packet, resulting in amplification. Respond with the last ACK packet the reflection service will continue to Single SYN-ACK packet to be delivered to the victim, when the victim does not While your typical three-way handshake might assume for a

Services at the reflection addresses reply with a SYN-ACK packet to the victim Spoofed SYN packet, with the original source IP replaced by the victim’s IPĪddress, to a wide range of random or pre-selected reflection IP addresses. In a TCP SYN-ACK reflection attack, an attacker sends a

Over the last two years, there has been a steady growth in attackers leveraging Instead, TCP attacks are leveraged to generate high packet rates (increased volumes of Packets Per Second – PPS) that require large amounts of resources from network devices to process the traffic and cause outages. In general, TCP attacks are low bandwidth and less likely to saturate an internet link. The lack of popularity was mainly due to the wrong assumption that TCP reflection attacks cannot generate enough amplification compared to UDP-based reflections. TCP reflection attacks, such as SYN-ACK reflection attacks, have been less popular among attackers until recently.

Response Team (ERT) have been monitoring and defending against an increasing Throughout 2019, Radware’s Threat Research Center (TRC) and Emergency

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